1. Field of the Invention
The present invention relates to a fluid spray nozzle, a pulverizer and a method of preparing toner.
2. Discussion of the Related Art
Fluidized-bed pulverizers preparing micron order powdery materials are known. The fluidized-bed pulverizer is formed of a plural pulverization nozzles, i.e., fluid spray nozzles, a pulverization chamber and a rotating classifier. In the fluidized-bed pulverizer, the nozzles are located so as to spray a fluid compressed gas toward the center of the pulverization chamber. The powdery materials fed in the pulverization chamber are accelerated toward the center of the pulverization chamber by the compressed gas sprayed from the pulverization nozzles. The powdery materials accelerated toward the center of the pulverization chamber collide against each other at the center thereof to be pulverized. The pulverized powdery materials are fed by an updraft generated at the center of the pulverization chamber to the rotating classifier located above the pulverization chamber. The powdery materials having a particle diameter less than a desired particle diameter are collected by the rotating classifier and returned to the pulverization chamber to be pulverized.
The conventional fluidized-bed pulverizer needs pulverizing repeatedly to prepare particles having a desired particle diameter, resulting in pulverization inefficiency.
Japanese published unexamined application No. 8-52376 discloses a pulverizer increasing the spray speed of a compressed gas from the pulverization nozzles to enhance the pulverization efficiency.
The pulverization nozzles disclosed in Japanese published unexamined application No. 8-52376 has a compressed gas feed nozzle feeding a compressed gas and an acceleration pipe accelerating the compressed gas fed from the compressed gas feed nozzle. The acceleration pipe has an expansion angle θ of some degree. The acceleration pipe having such a shape can well accelerate the compressed gas having passed a throat having the minimum sectional area when the nozzle is cut perpendicular to a traveling direction of the compressed gas to increase the speed of the compressed gas sprayed from the pulverization nozzles. As a result, the powdery material accelerated by the compressed gas sprayed from the pulverization nozzles increases in collision energy and has a desired particle diameter at one time collision pulverization, which increases pulverization efficiency.
As a result of keen studies of the present inventors, they found nozzle conditions having a speed faster than that of the pulverization nozzles disclosed in Japanese published unexamined application No. 8-52376. Namely, as for the pulverization nozzles disclosed therein, the nozzle conditions through which a compressed gas flows to the throat are not studied at all. While the compressed gas flows thereto, the gas loses a pressure and a speed. Consequently, the compressed gas does not have enough speed at the throat and does not, either even when accelerated by the acceleration pipe. Therefore, the compressed gas sprayed from the pulverization nozzles does not have enough speed.
Because of these reasons, a need exists for a fluid spray nozzle capable of spraying a fluid at sufficient speed.